[dependabot]

Bumps @langchain/core from 1.2.17 to 1.3.0.

Release notes

Sourced from @​langchain/core's releases.

@​langchain/core@​1.3.0

Minor Changes

• #11986 2caf64d Thanks @​richardscarrott! - feat: stream tool-call args as tool-call-delta slices

  Tool-call and server-tool-call args now stream as tool-call-delta events, which carry only the new slice of the args, instead of block-delta snapshots of the args so far. A large tool call now costs about the same bytes on the wire as the same length of text.

  • This covers the compat bridge (any model that only implements _streamResponseChunks), the OpenAI-compatible converter (OpenAI Completions, Groq, Mistral, IBM, OpenRouter, Perplexity, DeepSeek, Fireworks, Together AI and xAI Completions), OpenAI and xAI Responses, Anthropic (client and server tool calls) and Bedrock Converse. Google and Ollama still send one complete snapshot per call.
  • A tool call's id, name and index go on content-block-start, which carries no args. An id or name that arrives later reaches consumers on content-block-finish.
  • If you read raw events and their block-delta fields.args mid-stream, or write agent stream transformers that do, read tool-call-delta instead. await stream, .toolCalls and the assembled message are unchanged.
  • Upgrade your clients first. Older clients mishandle tool-call-delta. You need @langchain/langgraph-sdk 1.12.6 or later; @langchain/react, @langchain/vue, @langchain/svelte or @langchain/angular 1.2.6 or later; and langchain-core 1.6.13 or later for Python clients.
  • To hold back, pin @langchain/core below 1.3.0. That also keeps you on @langchain/openai, @langchain/anthropic, @langchain/aws and @langchain/xai versions that send snapshots.

@​langchain/core@​1.2.20

Patch Changes

• #11922 d71c542 Thanks @​richardscarrott! - feat(core): add midConversationSystemMessages and midConversationTools to ModelProfile. They say whether a chat model sends a system message after the first turn in place, and whether it can add a tool through a message rather than the request's tool list. Either way the prompt prefix before it stays unchanged.

@​langchain/core@​1.2.19

Patch Changes

• #11982 5af4684 Thanks @​richardscarrott! - feat(core): read tool-call-delta in ChatModelStream

  • ChatModelStream appends tool-call-delta slices to a tool call's args, and still replaces them on block-delta
  • It ignores delta types it doesn't recognize instead of throwing Unknown delta type

@​langchain/core@​1.2.18

Patch Changes

• #11956 93d62b0 Thanks @​hntrl! - Require langsmith >=0.11.0 to include the restored NullableHeaders type declarations.

• #11822 d3e6fe6 Thanks @​dqbd! - Add explicit agent address support to LangChainTracer, inherit project and address destinations together, and delegate default destination resolution to the LangSmith SDK.

• #11150 cea15cf Thanks @​mdnanocom! - fix(core): defer tool call chunk collapsing in AIMessageChunk to fix O(n²) streaming aggregation

  AIMessageChunk eagerly re-ran collapseToolCallChunks in its constructor on every streamed delta concat, re-parsing all accumulated tool args each time — O(n²) over a stream, which can block the event loop for seconds on long tool-call streams. Collapsing now runs lazily, once, on first read of tool_calls / invalid_tool_calls.

Commits

• 38eb4d8 chore: version packages (#12018)
• dae3b1f chore(core): fill in client versions in tool-call-delta changeset (#12019)
• 2caf64d feat(core,openai,anthropic,aws,xai): stream tool-call args as `tool-call-delt...
• 8a008ea test(core): accept either order of a chunk's stream events in chat model chai...
• f65acc3 chore(deps): restore missing @modelcontextprotocol/core@2.3.0 lockfile entr...
• 6a0ab38 chore: version packages (#12008)
• 654c7c6 chore(deps-dev): bump @​modelcontextprotocol/server from 2.3.0 to 2.3.1 (#12005)
• f096a32 fix(langchain): deliver final answers after todo updates (#11989)
• c690992 fix: update Node.js to October 2026 security release (#12007)
• 0c5e7bc fix(langchain): avoid full-state copies in parallel tool tasks (#11990)
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